Lack of a crystal ball frustrates scientists

Senior seismologist Clive Collins was on duty when the first signals from Tuesday's Christchurch earthquake registered on computer screens at Geoscience Australia's Canberra operations centre.

Collins and colleagues at the federal government agency could tell Christchurch had been hit by a devastating quake. The lines tracing ground movement, detected by seismographs on New Zealand's South Island, told a story of destruction. Collins says it is unclear whether Tuesday's quake was an aftershock of the September one. Aftershocks, which can continue for years, are caused when the crust relieves stresses set up by the original earthquake, he says: "The rock settles back into equilibrium."

A team including Gordon Lister, a professor in structural geology and tectonics at the Australian National University's research school of earth sciences, is conducting research it hopes could lead to earthquake forecasting. The method would use global positioning systemsatellite information to detect the tiny vertical motions in the Earth's surface that reflect the acceleration of the build-up of stress that precedes the ruptures on faults that lead to earthquakes. The scientists are using sophisticated computer models to process the GPS data. "The modelling leads to predictions on where the stress is building up," Lister says.